The present invention generally relates to fluidtight connections between tubes, pipes and the like and various tube assembly blocks such as manifolds. More specifically, the invention relates to fluidtight beaded connections between tube blocks and relatively thin-walled tubing.
Prior efforts at forming a fluidtight beaded tube connection typically have used an o-ring compressed by the tube bead against a tube block wall or counterbore. Such a design is disclosed in U.S. Pat. No. 3,778,090 issued to Tobin. However, there are numerous problems associated with this technique. Among them is the fact that the bead itself is used as one of the sealing surfaces, but unfinished tubing does not provide a good sealing interface even with an o-ring type seal. The contour and configuration of the bumped bead is difficult to control for repeatability and predictability. Also, since the bump is formed in direct contact with the o-ring there is a substantial risk of pinching or cutting the o-ring, or failing to properly compress the o-ring due to a misformed bead. The inner surface of a counterbore is also typically scratched by the machining process. All of these conditions contribute to an unreliable seal against fluid leakage caused by poor o-ring/surface contact or incorrect compression of the o-ring seal.